? asked in Science & MathematicsChemistry · 1 month ago

# 60. What is the enthalpy of this reaction?

A total of 2.00 mol of a compound is allowed to react with water in a foam coffee cup and the reaction produces 127 g of solution. The reaction caused the temperature of the solution to rise from 21.00 to 24.70 ∘C. What is the enthalpy of this reaction? Assume that no heat is lost to the surroundings or to the coffee cup itself and that the specific heat of the solution is the same as that of pure water.

Enter your answer in kilojoules per mole of compound to three significant figures.

Relevance
• 1 month ago

Supposing the heat capacity of the solution is the same as pure water:

(4.184 J/g·°C) x (127 g) x (24.70 - 21.00)°C / (2.00 mol) = 983 J/mol = −0.983 kJ/mol

[The last minus sign did not come from the calculation. It is the convention for exothermic processes.]

• 1 month ago

heat absorbed by solution:

q = m c (T2-T1)

q = 127 g (4.184 J/gC) (24.70 - 21.00) = +1966 J

So, the reaction released +1966 J.

Delta H is normally expressed in kJ/mol. So,

1.966 kJ / 2.00 mol = +0.983 kJ/mol